This invention relates to an apparatus for measuring grain loss in harvesting machines. More particularly, this apparatus may be used for measuring grain losses occurring at the discharge end of grain handling mechanisms such as the threshing and separating mechanism or the cleaning apparatus of such harvesting machines. Lost grain is that grain which is lost by way of either being entrained in the straw which is discharged from the combine separating mechanism to the ground or by way of being discharged together with chaff and other impurities from the combine cleaning apparatus.
Throughout this specification the reference to "grain" is intended to refer to that part of the crop which is threshed and separated from the discardable part of the crop material which is referred to as "straw". In the following description terms such as "forward", "rearward", "left", "right" etc. are used which are words of convenience and which are not to be construed as limiting terms.
Grain loss monitors for harvesting machines are known in the art and these attempt to monitor the amount of grain which is lost by way of relying on impact detectors which "count" a fraction of the grain which is being discharged at the back of the machine. However, the operator is unable to determine the relative proportion between the fraction of grain which impacts upon the grain loss detector or detectors on the one hand and the total actual losses on the other hand. This gives rise to perhaps the most important problem associated with existing grain loss monitors to the extent that there is not available a monitor which will indicate, in absolute terms, the amount of grain being lost during the harvesting process. Known monitors have only been able to provide some indication which varies more-or-less proportionally with the variations in the magnitude of the actual grain losses.
However, the present invention does not address this particular problem but rather two further problems which equally are associated with known monitors. The first one of these further problems consists of the relatively complicated operation of known grain loss monitors while that the other one is concerned with the lack of accuracy in the measurements in as much as known monitors are unable to distinguish adequately between grain and straw; the latter problem being particularly critical when the crop material is relatively wet.
Regarding the problem of complexity of known grain loss monitors, a plurality of controls require operation by the operator in order to set the monitor for any given circumstance.
For example, there is one control which has to be set according to the type of crop being harvested. This control sets the signal threshold value which must be lower for relatively small grain and which must be higher for relatively large grain. This setting further also is particularly critical in connection with the second problem as will be explained later.
Another control sets the sensitivity of the monitor and should take into account the condition of the crop material being harvested. It may not always be easy to decide whether a crop is wet or dry, for example and, in any event, the conditions can change as the harvesting process progresses so that ideally the monitor settings should be adjusted accordingly.
A third control also has to be operated according to whether a detector being monitored is associated with either the separating mechanism and/or the cleaning sieves of the harvesting machine.
The setting of these controls takes time and experience as, in practice, it requires a relatively complex procedure. In accordance with this procedure, the operator has to calibrate the monitor for each one of the settings of the third control, i.e. the control for selecting between the detectors associated with the separating mechanism and/or the cleaning sieves. As a first step in these calibrating procedures, the operator has to set the first control, i.e. the control of the signal threshold value in accordance with the type of crop material to be harvested. This control should be set sufficiently low so that impacts occasioned by grain kernals on the detector or detectors generate signals in the circuitry associated with these detector or detectors. This thus varies with the specific weight of the grain being harvested.
Next, the operator has to operate the harvester at a capacity rate which he expects to correspond to the grain loss rate which he considers to be just within the acceptable limits. He then sets the second control, i.e. the control for setting the monitor sensitivity so that an appropriate monitor "reading" is generated. Next, he physically checks the straw, chaff and other debris which is being discharged by the machine and he uses his practiced eye to decide whether or not the extent of grain loss that actually occurs is indeed at the rate he has choosen to be acceptable. If it is not, then a further test run is made at a different capacity rate which is expected to entrain the grain loss rate which is acceptable. The second control is reset to generate an appropriate monitor "reading" and the physical checking of the material issuing from the harvester is repeated. These steps are repeated until on the one hand, the maximum capacity rate for a given grain loss rate, which is considered still to be acceptable, is obtained and, on the other hand, the second control is set so as to generate a monitor "reading" which is adequate at this acceptable grain loss rate.
When the operator decides that the grain loss is at the acceptable rate, he then attempts to operate the machine so as to keep the grain loss monitor "reading" at the same value. If the operator does not use his practiced eye to effect this calibration of a know grain loss monitor, then grain loss can be relatively high even when the monitor might indicate otherwise. Also, the opposite may be true in as much as the grain loss monitor possibly could indicate that there is grain loss which, whilst being true, is at a level which is significantly less than is considered to be acceptable. This would unnecessarily curtail the harvester capacity. This calibration is particularly difficult because actual quantification of the grain loss rate by a mere physical control of the material discharged at the back of the harvester is not possible and this is why the practiced eye of the operator is required for the calibration. The complexity of this calibration is also the main reason why the controls of known monitors tend to be left alone by the operator with a result that known grain loss monitors are of little practical use.
Also, even if the controls are operated in a proper manner, the indicated grain loss still suffers from the problem of being inaccurate in that the or each detector cannot always adequately distinguish between impacts from straw as opposed to impacts from grain. This difficulty arises because the stems of a given crop have nodules or knobs along their length and very often stems will break at these nodules. This gives rise to pieces of straw having a nodule at one end. If such a piece of straw impacts a detector with the nodule leading, then it can give rise to a signal somewhat similar to that created by the impact of a grain kernal. Accordingly, the detector counts such impacting pieces of straw as grain kernals and will thus indicate a greater grain loss than is actually occurring with the result that the operator may change the operating conditions to reduce the grain loss to what he decides is an acceptable level and which he may already be achieving. One operating condition which may be changed to this end is the forward speed of the machine which may be reduced and which thus increases the harvesting time with the attendant expense and yet often is unnecessary in as much as actual grain loss may be within the range which is acceptable to the operator.
Discrimination between impacts occasioned by grain kernals and pieces of straw may be obtained in known grain loss monitors by adjusting the first control, i.e. the control for setting the signal threshold value. Ideally, this control should be set so that the monitor records all grain kernal impacts on the one hand and eliminates all straw impacts on the other hand. However, it has been found that, in practice, a monitor "reading" quite often is generated in part by straw impacts and in part by grain kernal impacts. However, it is very difficult, if not totally impossible, for the operator to accurately assess what part of the monitor "reading" is generated by straw impacts and what other part of the monitor "reading" is generated by the grain kernal impacts.
This problem is even further aggravated by the fact that the point of discrimination between grain kernal impacts and straw impacts greatly fluctuates dependent on the crop conditions such as the moisture content of the crop material being harvested. Wet crop conditions require a lower threshold setting than dry crop conditions because of the relative softness of wet grain kernals and pieces of straw. A threshold setting which is acceptable for dry crop conditions, i.e. which adequately discriminates between dry grain kernals and dry pieces of straw may be too high for detecting impacts of wet grain kernals. Also, an acceptable setting for wet crop conditions may read impacts occasioned by pieces of dry straw as grain kernal impacts. As a consequence, it thus is also very difficult for the operator to decide on the threshold setting of the monitor. The foregoing problems further also are complicated by the fact that, on the one hand, in dry crop conditions the straw is much more brittle. This results in much more pieces of straw with a nodule at one end being formed. Accordingly, in dry crop conditions, also a relatively higher proportion of the impacts received on the grain loss detectors are caused by pieces of straw. On the other hand, it also is much more difficult, in wet crop conditions, for grain kernals to be separated from the layer of straw which is discharged at the rear end of the harvester and thus, proportionally, a smaller number of grain kernals impact on the detectors in wet crop conditions even though the grain loss level may be high.
In view of the high cost of a harvesting operation, it is extremely important to maximize the capacity of a given harvesting machine, consistent with achieving a grain loss rate which does not exceed a set limit.